The present invention relates to a windshield wiper driving device for wiping the surface of a window and, more particularly, to a concealed or semi-concealed type window wiper driving device having a function to partially conceal a wiper blade from view when it is stopped.
According to one example of the constructions known in the prior art, as is disclosed in Japanese Utility Model Publication No. 42-10969, the output shaft of a drive motor is made to perform an eccentric motion when in the concealing operation so that a connecting lever is moved with a stroke longer than the usual stroke. In another example disclosed in Japanese Utility Model Publication No. 44-17930, a reversible drive motor is used, and an eccentric bearing is arranged at a portion jointing a connecting lever and a crank arm at the side of the drive motor so that the substantial length of the connecting lever may be changed in accordance with the forward and backward rotations of the eccentric bearing.
However, the former construction has defects: that, in order to make eccentric the output shaft of the drive motor, the transmission of the driving force is once released to effect one half rotation of the eccentric bearing, while fixing the position of a crank arm, so that the front shield cannot be instantly wiped clean, when the switch is turned on with the wiper blade being left stopped; and that its internal construction is so complex that its production cost is necessarily raised.
On the other hand, the latter construction can be appreciated in its high simplicity at the eccentric bearing jointing the connecting lever and the crank arm but still has defects: that it is necessary at present in a permanent magnet type motor to use a plurality of relays for effecting the forward and backward rotations and to give a special construction to a device for effecting the stop at a fixed position, thus inviting a disadvantage in the production cost; and that the upwardly reversed position of the blade before it is concealed is located inside of the usual wiping range so that the shield has its surface left blotted, thus deteriorating the view after the wiper is stopped.